At his customer's invitation, he travelled to Guangzhou to check out the item and found that it was 'not right'. He took a few samples of the material from the workshop where the statue was carved and brought them back to Singapore for a more in-depth analysis.
His suspicions were confirmed - the material turned out to be green feldspar, not jade.
As a result, he saved his customer from being conned into buying a US$10 million (S$17 million) 'jade' statue that was probably worth only about US$500,000.
That was in 2002, 14 years after the 55-year-old gemstone expert set up Far East Gemological Laboratory.
Located at Orchard Towers, the modest outfit offers services such as gem identification, diamond grading and jewellery appraisal.
Mr Tay, who graduated from the Gemological Institute of America in 1980 and holds a bachelor's degree in geology from the University of London, was president of the Singapore Gemologist Society from 1993 to 2003.
He also conducts training for the staff of auction houses and jewellery shops.
However, of all the activities he is involved in, he enjoys gemstone research the most.
All that research has led him having 35 research papers published over the last 25 years. They have appeared in gemological journals in the United Kingdom, the United States of America and Australia.
He has also been invited to share his research findings at international symposia and conferences in countries such as Japan, Thailand, China, Germany and Switzerland.
In 2000, for instance, he represented Singapore at the Asia-Pacific Economic Cooperation (APEC) International Jewellery Conference in Melbourne, and the APEC Gems and Jewellery Trade and Technology seminar in Beijing.
Mr Tay emphasized that research was important in developing better ways of telling the real stuff from the fake, and also to find answers to questions that customers would ask.
He said: 'In order to authenticate gemstones, especially with new chemically treated stones coming into the market, we have to do extensive research.'
He has partnered institutions such as the National University of Singapore and Singapore Polytechnic (SP) for research purposes. In the early 1990s, for example, he collaborated with SP to come up with a method to tell natural jade from chemically-treated or lower-grade jade.
Since he was young, Mr Tay has always loved identifying rocks and minerals.
He recalled: 'My parents owned a timber business and I used to go into the jungle where the employees worked. I would collect plants and rocks and put them in my pockets and in bags. My house became like a junkyard! Even now, I have lots of mineral specimens all over the place!'
In fact, the proud collector was eager to show off the prized possessions in his laboratory. He displayed a nondescript brownish-grey rock, half the size of a soccer ball, and said it was 'dinosaur dung'.
Next, he whipped out a tiny rectangular slab of metal dotted with yellow sparkles, identifying it as a meteorite sample from Argentine. It was the size of two mobile phone SIM cards.
Mr Tay has also travelled overseas to carry out research. For instance, in 2002, he visited southeast Kalimantan to study its diamond mining operations and find out why diamonds were formed the way they were.
Other than research for pure interest, he also did it to provide his customers with a more comprehensive service.
He said: 'If you study diamonds from a certain locality, and customers come to your shop with diamonds from there, you can give a more complete explanation to them, like why their diamonds look a certain way.'
He feels a sense of achievement when he manages to keep his customers avoid fakes or pay more than what is necessary.
He said: 'When the results confirm that I was correct and I helped the customer, I feel very satisfied.'
Photo caption: His interest in gemstone research has led Mr Tay all over the world to share his findings at international conferences.
By Dawn Wong.